Leptospirosis is a zoonotic disease of worldwide distribution and importance. The chief hosts of leptospires in wildlife include deer, foxes, raccoons, skunks, opossums, muskrats, mongooses, and rodents. Domestic animals harboring leptospires include horses, cattle, goats, pigs, and sheep. Dogs may become infected and develop illness, although infections in cats are extremely rare. Humans are considered incidental hosts and can develop illness that ranges from mild, self-limiting symptoms to multi-organ failure in severe cases.
Humans acquire leptospires directly from animals, and indirectly from occupational or recreational exposure to urine-contaminated water or environmental surfaces.1 Rats and other rodents are the most common zoonotic source.2 Leptospires enter the blood stream through imperfections in the skin, through mucous membranes, or by the ingestion of contaminated water. The urine of infected animals and humans may contain 106 to 108 microorganisms per milliliter, and leptospires may be shed into the environment up to 3 months after clinical recovery from disease.